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11/06 Miscellaneous Sources 13.2.4-1

13.2.4 Aggregate Handling And Storage Piles

13.2.4.1 General

Inherent in operations that use minerals in aggregate form is the maintenance of outdoorstorage piles. Storage piles are usually left uncovered, partially because of the need for frequentmaterial transfer into or out of storage.

Dust emissions occur at several points in the storage cycle, such as material loading onto thepile, disturbances by strong wind currents, and loadout from the pile. The movement of trucks andloading equipment in the storage pile area is also a substantial source of dust.

13.2.4.2 Emissions And Correction Parameters

The quantity of dust emissions from aggregate storage operations varies with the volume ofaggregate passing through the storage cycle. Emissions also depend on 3 parameters of the conditionof a particular storage pile: age of the pile, moisture content, and proportion of aggregate fines.

When freshly processed aggregate is loaded onto a storage pile, the potential for dust emissionsis at a maximum. Fines are easily disaggregated and released to the atmosphere upon exposure to aircurrents, either from aggregate transfer itself or from high winds. As the aggregate pile weathers,however, potential for dust emissions is greatly reduced. Moisture causes aggregation and cementationof fines to the surfaces of larger particles. Any significant rainfall soaks the interior of the pile, andthen the drying process is very slow.

Silt (particles equal to or less than 75 micrometers [:m] in diameter) content is determined bymeasuring the portion of dry aggregate material that passes through a 200-mesh screen, usingASTM-C-136 method.1 Table 13.2.4-1 summarizes measured silt and moisture values for industrialaggregate materials.

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13.2.4-2

EMISSIO

NFACTORS

1

1

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Table 13.2.4-1. TYPICAL SILT AND MOISTURE CONTENTS OF MATERIALS AT VARIOUS

IndustryNo. OfFacilities Material

Silt Content (%)

No. OfSamples Range Mean

NSa

Iron and steel production 9 Pellet ore 13 1.3 - 13 4.3Lump ore 9 2.8 - 19 9.5

Coal 12 2.0 - 7.7 4.6

Slag 3 3.0 - 7.3 5.3

Flue dust 3 2.7 - 23 13

Coke breeze 2 4.4 - 5.4 4.9

Blended ore 1 15

Sinter 1 0.7

Limestone 3 0.4 - 2.3 1.0

Stone quarrying and processing 2 Crushed limestone 2 1.3 - 1.9 1.6

Various limestone products 8 0.8 - 14 3.9

Taconite mining and processing 1 Pellets 9 2.2 - 5.4 3.4Tailings 2 ND 11

Western surface coal mining 4 Coal 15 3.4 - 16 6.2

Overburden 15 3.8 - 15 7.5

Exposed ground 3 5.1 - 21 15

Coal-fired power plant 1 Coal (as received) 60 0.6 - 4.8 2.2

Municipal solid waste landfills 4 Sand 1 2.6

Slag 2 3.0 - 4.7 3.8

Cover 5 5.0 - 16 9.0

Clay/dirt mix 1 9.2

Clay 2 4.5 - 7.4 6.0

Fly ash 4 78 - 81 80Misc. fill materials 1 12

a References 1-10. ND = no data.

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11/06 Miscellaneous Sources 13.2.4-3

13.2.4.3 Predictive Emission Factor Equations

Total dust emissions from aggregate storage piles result from several distinct source activitieswithin the storage cycle:

1. Loading of aggregate onto storage piles (batch or continuous drop operations).2. Equipment traffic in storage area.

3. Wind erosion of pile surfaces and ground areas around piles.4. Loadout of aggregate for shipment or for return to the process stream (batch or continuous

drop operations).

Either adding aggregate material to a storage pile or removing it usually involves dropping thematerial onto a receiving surface. Truck dumping on the pile or loading out from the pile to a truckwith a front-end loader are examples of batch drop operations. Adding material to the pile by aconveyor stacker is an example of a continuous drop operation.

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13.2.4-4 EMISSION FACTORS 11/06

The quantity of particulate emissions generated by either type of drop operation, per kilogram(kg) (ton) of material transferred, may be estimated, with a rating of A, using the following empiricalexpression:11

where:

E = emission factork = particle size multiplier (dimensionless)U = mean wind speed, meters per second (m/s) (miles per hour [mph])M = material moisture content (%)

The particle size multiplier in the equation, k, varies with aerodynamic particle size range, as follows:

Aerodynamic Particle Size Multiplier (k) For Equation 1

< 30 :m < 15 :m < 10 :m < 5 :m < 2.5 :m

0.74 0.48 0.35 0.20 0.053a

aMultiplier for < 2.5 :m taken from Reference 14.

The equation retains the assigned quality rating if applied within the ranges of sourceconditions that were tested in developing the equation, as follows. Note that silt content is included,even though silt content does not appear as a correction parameter in the equation. While it isreasonable to expect that silt content and emission factors are interrelated, no significant correlation

between the 2 was found during the derivation of the equation, probably because most tests with highsilt contents were conducted under lower winds, and vice versa. It is recommended that estimates fromthe equation be reduced 1 quality rating level if the silt content used in a particular application fallsoutside the range given:

Ranges Of Source Conditions For Equation 1

Silt Content(%)

Moisture Content(%)

Wind Speed

m/s mph

0.44 - 19 0.25 - 4.8 0.6 - 6.7 1.3 - 15

To retain the quality rating of the equation when it is applied to a specific facility, reliablecorrection parameters must be determined for specific sources of interest. The field and laboratory

procedures for aggregate sampling are given in Reference 3. In the event that site-specific values for

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13.2.4-6 EMISSION FACTORS 11/06

10. Chicago Area Particulate Matter Emission Inventory Sampling And Analysis, EPA ContractNo. 68-02-4395, Midwest Research Institute, Kansas City, MO, May 1988.

11. Update Of Fugitive Dust Emission Factors In AP-42 Section 11.2, EPA ContractNo. 68-02-3891, Midwest Research Institute, Kansas City, MO, July 1987.

12. G. A. Jutze, et al., Investigation Of Fugitive Dust Sources Emissions And Control,

EPA-450/3-74-036a, U. S. Environmental Protection Agency, Research Triangle Park, NC,June 1974.

13. C. Cowherd, Jr., et al., Control Of Open Fugitive Dust Sources, EPA-450/3-88-008,U. S. Environmental Protection Agency, Research Triangle Park, NC, September 1988.

14. C. Cowherd,Background Document for Revisions to Fine Fraction Ratios &sed for AP-42Fugitive Dust Emission Factors. Prepared by Midwest Research Institute for WesternGovernors Association, Western Regional Air Partnership, Denver, CO, February 1, 2006.